In the case of known columns comprising structured packings and/or random packings, these are held in the column by at least one support tray. The liquid is distributed as uniformly as possible over the bed of structured packings or bed of random packings at the feed point or the reflux point by means of a liquid distributor tray. The structured packings or the random packings rest on the support tray. The column has, as a rule, a plurality of beds of structured packings or random packings. Between two successive beds of structured packings or random packings, the liquid must be distributed as uniformly as possible over the bed underneath. Liquid collectors are used for collecting liquid, for example on a bed underneath, or for removing liquid, for example from the column. Thus, in known columns comprising structured packings and/or random packings, support trays, liquid distributors, liquid redistributors and/or liquid collectors are used as individual trays.
For corrosion-resistant plant construction, in particular for the diameter range from 600 mm to over 2000 mm, enamel columns are used.
For design reasons, the internals for the columns (liquid distributor, liquid redistributor, liquid collector and mass transfer tray) are manufactured from materials other than steel/enamel. The support trays constitute an exception. Support trays which are in the form of slotted trays and whose slotted plate is enamelled on both sides are known. These known steel/enamel support trays have a free cross-section of only about 40%, based on the total column cross-section. This small free cross-section has the considerable disadvantage that no high gas loads (F factors greater than 1.8) and liquid loads (greater than 40 m3/m2h) can be run in the column, although this would be possible with modern structured packings and random packings.
It is known that constructions of tantalum or ceramic can be used to enable high gas loads (F factors greater than 1.8) to be run in the column. However, ceramic has less corrosion resistance than glass and enamel. Tantalum constructions are considerably more expensive than steel/enamel constructions.
In order to provide large flow cross-sections from the gas flow in the case of columns having a high gas throughput, U.S. Pat. No. 4,028,442 discloses that a column tray which is not flat should be provided for a column having a high gas throughput. In order to increase the flow cross-section for the gas throughput, the column tray has a grid which is undulating or formed with inclined or perpendicular sections and is supported on a support structure in the column. Owing to the inclined or perpendicular shape of the grid with the orifices formed therein for the gas flow, the flow cross-section is greater than in the case of a flat embodiment of the grid.
U.S. Pat. No. 5,281,369 discloses column trays having a grid which is undulating or is arranged on a support structure. The grid is formed in such a way that the gas stream passes through the region of the wave summits while the liquid is collected in the valleys and emerges downwards through small holes. Since the gas stream and the liquid stream are passed along substantially separate routes through the column tray, a higher gas flow rate can be achieved with the same liquid throughput.
These known column trays have the disadvantage that they cannot be produced without considerable costs for corrosion-resistant materials. In addition, a support structure for the grids is required in the case of the known column trays.
German Offenlegungsschrift 1 262 225 discloses a mass transfer tray in which the bubble-caps can be inserted into the tray by simply pressing in.
German Offenlegungsschrift DE 36 04 013 A1 describes a large-size corrosion-resistant mass transfer tray which consists of a glass fibre-reinforced core which is surrounded by a thin corrosion-resistant covering of PVDF. Holes for bubble-caps are provided in the tray.
German Offenlegungsschrift DE 29 43 687 A1 discloses a column tray according to the precharacterizing clause of claim 7.
The liquid distributor shown in one or more of the foregoing references has an area which is smaller than the cross-section of the column so that the gas can pass through upwards adjacent to the tray, and the free cross-section is therefore relatively large. A collector must therefore be provided above the liquid distributor in order to apply the liquid to the liquid distributor. Moreover, a support for the tray must be provided.